If x 2 (x3-5x2+ax+b ) ( x-1-1 ) e(x-1)=m, then a+b+m is equal to :
- 5
- 6
- 8
- 10
Answer
(2) 6
Solution
Put x=2+h, h 0:
x-1-1= 1+h-1= h 1+h+1 h2 and e(x-1)= e(1+h) h
∴ Denominator h22= (x-2)22
Let p(x)=x3-5x2+ax+b. For a finite limit, p(x) 0 like (x-2)2, so (x-2)2 divides p(x):
p(2)=0 8-20+2a+b=0 2a+b=12
p'(2)=0 12-20+a=0 a=8, b=-4
p(x)=x3-5x2+8x-4=(x-1)(x-2)2
∵ p(x) p(x) as p(x) 0:
m= x 2 (x-1)(x-2)2(x-2)2/2=2(2-1)=2
∴ a+b+m=8-4+2=6
Answer: (2)